Effects of Helicobacter pylori on the expression of catalytic subunit of the DNA-dependent protein kinase and Ku70/Ku80 heterodimer in gastric mucosa epithelial cells in vivo and in vitro

Abstract

Objective To explore the effects of Helicobacter pylori (H.pylori) on the expression of catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) and Ku70/Ku80 heterodimer in gastric mucosa epithelial cells in vivo and in vitro.Methods After treated with H.pylori for one,three,six,12 and 24 hours,the expressions of DNA-PKcs and Ku70/Ku80 heterodimer in gastric epithelial cells (GES) 1 and gastric adenocarinoma cells (AGS) were detected by Western blot.Mongolian gerbils were gavaged with H.pylori,and were sacrificed after infected for six and 12 months.The gastric mucosa tissues were taken for immunohistochemistry to detect the expressions of DNA-PKcs and Ku70/Ku80 heterodimer at protein level.The data were analyzed by t test and chi-square test.Results After H.pylori infection for one hour,the relative quantity of the expression of DNA-PKcs in GES-1 was 1.16±0.09,which was higher than that of non infected group (1.04±0.31) and the difference was statistically significant (t=4.67,P＜0.05).After infected by H.pylori for one,three,six,12 and 24 hours,the relative quantities of the expressions of Ku70/Ku80 heterodimer in GES-1 were 1.58±0.32,1.84±0.40,1.97±0.35,3.72±1.42 and 3.74±1.56,respectively,all were higher than that of non infected group (1.24±0.31) and the differences were statistically significant (t=3.57,4.20,5.03,8.11 and 8.14,all P＜0.05).The relative quantities of the expressions of Ku70/Ku80 heterodimer in AGS were 4.69 ± 0.87,3.67 ± 0.67,2.41±0.24,1.35±0.35 and 1.32±0.10 after H.pylori infected for one,three,six,12 and 24 hours,respectively,all were lower than that of no H.pylori infected group (4.84 ± 0.76) and the differences were statistically significant (t=34.13,27.68,19.81,4.47 and 5.69,all P＜0.05).In Mongolian gerbil models,DNA-PKcs did not express in H.pylori negative group (0/25),the total positive rate of H.pylori infected group was 98.1％ (53/54),the difference between the two groups was statistically significant (x2 =74.55,P＜0.01).The total positive rate of Ku70/Ku80 heterodimer in H.pylori negative group was 92.0％ (23/25) and in H.pylori infected group was 68.5％ (37/54),the difference between the two groups was statistically significant (x2=5.16,P＜0.05).Conclusion H.pylori infection affected cellular DNA damage repair through changing the expression of DNA-PKcs and Ku70/Ku80 heterodimer in gastric mucosa in vivo and in vitro,which may cause gastric mucosal lesions. Key words: DNA-binding proteins; Catalytic domain; Protein kinases; Fibrin fibrinogen degradation products; DNA damage; Helicobacter pylori; Gerbillinae